Actomyosin-like, actin-like and myosin-like proteins have been isolated from mammalian brain. The objectives of this proposal are to continue our studies on the isolation, purification, and biochemical and physical characterization of these proteins isolated from synaptosomal subcellular preparations. These studies include SDS-polyacrylamide gel electrophoretic studies, amino acid composition, enzyme kinetics, and electron microscope examination by negative staining. The Ca 2 ion-sensitive protein component associated with the actomyosin system will be studied to determine whether it is associated with the actin or myosin and whether it is similar to muscle troponin-tropomyosin. Effect of drugs such as halothane on the protein system will also be investigated.